The wall thickness of a pipe or tube used in plant equipment deteriorates over time. The wall thickness remaining in the pipe is an important parameter in evaluating the equipment's suitability for service. Currently, the remaining wall thickness of a pipe is determined by sampling the wall thickness at selected positions along the pipe using ultrasonic thickness gauges. Because the reliability of this sampling approach depends greatly on the statistical validity of the samples, the results of such an evaluation are subject to considerable uncertainty. This is particularly true when the number of samples is small because of the high cost of acquiring data. For example, data acquisition becomes expensive when there is too much surface area to cover. Further, the number of samples can be small because of limited accessibility to the pipe, such as when the pipe is under insulation or bundled together with other pipes.